Low Update Rate Research Articles

Long baseline navigation with explicit pseudo-range clock offset and propagation speed estimation

This paper proposes a novel one-way-travel-time (OWTT) long baseline (LBL) navigation concept that departs from previous approaches in that: (i) the clock of the receiver in the vehicle needs not to be synchronized with the clocks of the emitters; and (ii) the speed of propagation of the signals is assumed unknown. The nonlinear system dynamics are considered in a continuous-discrete time framework, taking advantage of the pseudo-range measurements obtained at low update rates and the data from other sensors obtained at high rates. An augmented system is proposed whose observability is analyzed and that is shown to be equivalent to the original nonlinear system under appropriate conditions. A Kalman filter provides the estimation solution, with globally exponentially stable error dynamics, in spite of the original nonlinear nature of the system dynamics. The performance of the proposed solution is evaluated with numerical simulations resorting to Monte Carlo runs. The comparison with the extended Kalman filter and the Bayesian Cramér-Rao bound are also included.

Per-Contact Iteration Method for Solving Contact Dynamics

This letter introduces a new iterative method for contact dynamics problems. The proposed method is based on an efficient bisection method which iterates over each contact. We compared our approach to two existing ones for the same model and found that it is about twice as fast as the existing ones. We also introduce four different robotic simulation experiments and compare the proposed method to the most common contact solver, the projected Gauss-Seidel (PGS) method. We show that, while both methods are very efficient in solving simple problems, the proposed method significantly outperforms the PGS method in more complicated contact scenarios. Simulating one time step of an 18-DOF quadruped robot with multiple contacts took less than 20 μs with a single core of a CPU. This is at least an order of magnitude faster than many other simulators which employ multiple relaxation methods to the major dynamic principles in order to boost their computational speed. The proposed simulation method is also stable at 50 Hz due to its strict adherence to the dynamical principles. Although the accuracy might be compromised at such a low update rate, this means that we can simulate an 18-DOF robot more than thousand times faster than the real time.

A Physics-Based Vibrotactile Feedback Library for Collision Events.

We present PhysVib: a software solution on the mobile platform extending an open-source physics engine in a multi-rate rendering architecture for automatic vibrotactile feedback upon collision events. PhysVib runs concurrently with a physics engine at a low update rate and generates vibrotactile feedback commands at a high update rate based on the simulation results of the physics engine using an exponentially-decaying sinusoidal model. We demonstrate through a user study that this vibration model is more appropriate to our purpose in terms of perceptual quality than more complex models based on sound synthesis. We also evaluated the perceptual performance of PhysVib by comparing eight vibrotactile rendering methods. Experimental results suggested that PhysVib enables more realistic vibrotactile feedback than the other methods as to perceived similarity to the visual events. PhysVib is an effective solution for providing physically plausible vibrotactile responses while reducing application development time to great extent.

Fiber Bragg gratings-based sensing for real-time needle tracking during MR-guided brachytherapy.

The development of MR-guided high dose rate (HDR) brachytherapy is under investigation due to the excellent tumor and organs at risk visualization of MRI. However, MR-based localization of needles (including catheters or tubes) has inherently a low update rate and the required image interpretation can be hampered by signal voids arising from blood vessels or calcifications limiting the precision of the needle guidance and reconstruction. In this paper, a new needle tracking prototype is investigated using fiber Bragg gratings (FBG)-based sensing: this prototype involves a MR-compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. This stylet can be inserted into brachytherapy needles and allows a fast measurement of the needle deflection. This study aims to assess the potential of FBG-based sensing for real-time needle (including catheter or tube) tracking during MR-guided intervention. First, the MR compatibility of FBG-based sensing and its accuracy was evaluated. Different known needle deflections were measured using FBG-based sensing during simultaneous MR-imaging. Then, a needle tracking procedure using FBG-based sensing was proposed. This procedure involved a MR-based calibration of the FBG-based system performed prior to the interventional procedure. The needle tracking system was assessed in an experiment with a moving phantom during MR imaging. The FBG-based system was quantified by comparing the gold-standard shapes, the shape manually segmented on MRI and the FBG-based measurements. The evaluation of the MR compatibility of FBG-based sensing and its accuracy shows that the needle deflection could be measured with an accuracy of 0.27 mm on average. Besides, the FBG-based measurements were comparable to the uncertainty of MR-based measurements estimated at half the voxel size in the MR image. Finally, the mean(standard deviation) Euclidean distance between MR- and FBG-based needle position measurements was equal to 0.79 mm(0.37 mm). The update rate and latency of the FBG-based needle position measurement were 100 and 300 ms, respectively. The FBG-based needle tracking procedure proposed in this paper is able to determine the position of the complete needle, under MR-imaging, with better accuracy and precision, higher update rate, and lower latency compared to current MR-based needle localization methods. This system would be eligible for MR-guided brachytherapy, in particular, for an improved needle guidance and reconstruction.

Physiological Organ Motion Prediction and Compensation Based on Multirate, Delayed, and Unregistered Measurements in Robot-Assisted Surgery and Therapy

Physiological motion makes performing a surgical or therapeutic procedure more difficult for the physician. In heart surgery, the heart is stopped as it is too difficult for the surgeon to follow the heart's beating motion and perform a surgical task. In radiation therapy, respiration causes the cancerous tissue to move, rendering the therapy less effective and possibly damaging to healthy tissue. This paper focuses on controlling a robot, which is used to perform the surgery or therapy, to compensate for the physiological motion along the surgical tool's axis such that the point of interest (POI) on the organ becomes stationary relative to the robot. The difficulty in creating such a system lies in the measurement of the POI's and robot's positions via different sensors that are unregistered, have different measurement rates, and have data acquisition and processing delays. This paper presents the Kalman-filter-based estimation of the organ motion despite the large data acquisition/processing delays and low update rates inherent in some measurements used for robot control in robot-assisted surgeries and therapies. This paper also proposes control systems that compensate for the organ motion despite the delayed, multirate, and unregistered sensor data allowing the physician to perform a therapeutic or surgical procedure with a teleoperated robot on a seemingly stationary POI.

Smart lighting control with workspace and ceiling sensors

We consider energy-efficient indoor lighting control for adapting to daylight and user presence changes. Light sensors located at ceiling luminaires and at workspace desks are used to provide illumination information feedback, along with user presence information from occupancy sensors at ceiling luminaires, to a lighting controller. The light sensors at the workspace transmit information at a lower update rate than the sensors at the ceiling. Using this sensing information, we propose a control method to adapt the dimming levels of the luminaires such that desired illumination levels are achieved at the workspace level. The performance of the proposed method is evaluated in an office lighting testbed.

Sinusoidal Frequency Modulation Sparse Recovery for Precession Rate Estimation Using Low-Frequency Long-Range Radar

Low-frequency long-range radars (LFLRRs) are assumed to lack the ability of extracting targets micro motion signature, due to their low and nonuniform track update rate, as well as the weak micro Doppler (m-D) owing to their large wave length. The recently proposed sinusoidal frequency modulated (SFM) Fourier transform can achieve a longer integral period gain, and consequently provides a new perspective for extracting weak m-D signature. However, its direct application is unavailable for LFLRRs, since their track update rate is very low and may not even be constant. This paper derives a new approach, named sinusoidal frequency modulation sparse recovery (SFMSR) for m-D analysis with LFLRR, by exploiting the micro motion spectrum sparsity in SFM signal space. SFMSR employs the Fourier modulation dictionary, which is determined only by the frequency in SFM signal space. Unlike other sparse representation-based methods whose dictionary is discretization of a 3-D space parameterized by the micro motion amplitude, frequency, and initial phase, the SFMSR reduces the m-D analysis to 1-D parameter optimization, and therefore can enhance the precision, stability, and computational efficiency simultaneously. The temporally correlated sparse Bayesian learning in SFM signal space is employed to decompose the signal and produce highly sparse solutions. The simulation results indicate that the proposed method outperforms the existing methods in accuracy and robustness, which can provide satisfactory performance even when the carrier frequency is 430 MHz and the average data rate is 0.5 Hz.

Applied Technology in Data Evaluation and Position Quality of ADS-B System

Automatic dependent surveillance-broadcast (ADS-B) is a totally new surveillance method, so before practically applied and operated in China, abundant tests and evaluations are necessary to validate the performance of ADS-B and guarantee the operational security. To solve the asynchronous problem among radar data, ADS-B data and real-time kinematic (RTK) data caused by different update rates, this paper proposes the technique of synchronizing multi-surveillance data by extrapolating from the data of low update rate to high update rate according to velocity and heading. Meanwhile, because radar data, ADS-B data and RTK data are expressed in different coordinates and cannot be compared each other, this article provides a method to unifying the coordinates of multi-surveillance data. By the analysis and evaluation, we can conclude that the performance of ADS-B is better than radar. Addtionally, the paper makes focus study on the position quality indicator and the encoding rules, and puts forward the conversion between the different rules. The paper provides the technical guide for the manufacturers and the airlines.

A Cost-Effective Sideslip Estimation Method Using Velocity Measurements From Two GPS Receivers

This paper demonstrates that the vehicle sideslip can be estimated through the kinematic relationship of velocity measurements from two low-cost GPS receivers. To compensate for the low update rate of low-cost GPS receivers, acceleration/angular rate measurements from an inertial measurement unit (IMU) are merged with the GPS measurements using an extended Kalman filter (EKF). Two technical challenges were addressed: 1) unsynchronized updates of the two GPS receivers and 2) significant delays in GPS velocity measurement. A stochastic observability analysis reveals that the proposed method guarantees the observability when a vehicle has nonzero yaw rates. Experimental verification shows that the vehicle sideslip is estimated regardless of surface friction levels under several maneuvers.

Robust Electromagnetic Control of Microrobots Under Force and Localization Uncertainties

Microrobots are promising tools for micromanipulation and minimally invasive interventions. Robust electromagnetic control of microrobots can be achieved through precisely modeled magnetic steering systems and accurate localization. Error-free modeling and position information, however, are not realistic assumptions, and microrobots need to be controlled under force and localization uncertainties. In this paper, methods to account for these types of uncertainties are presented. Initially, the uncertainties in electromagnetic force generation of a new class of manipulation systems are quantified. Subsequently, a drag-force uncertainty model for linear dynamics is proposed. This model can be employed for microrobots whose fluid dynamics are not well understood. A set of performance measures is introduced in the design of controllers, and a PID and a robust H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller are synthesized and evaluated through simulations. To demonstrate the capabilities of the synthesized controllers under localization and force uncertainties, low update rates are considered. The H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller can provably respect the performance measures under higher uncertainties than the PID controller, and its performance is further quantified through experiments in a prototype electromagnetic control system.

Passive Multirate Wave Communications for Haptic Interaction in Slow Virtual Environments

Haptic interaction in slow virtual environments (VEs) can become unstable due to the phase lag introduced in the control loop by the slow update rate of the VE. Increasing the physical damping and/or limiting the contact stiffness rendered to users can mitigate the destabilizing effect of the low VE update rate. However, large physical damping and compliant virtual contacts decrease the sense of presence in VEs, especially during interaction with rigid virtual objects. To increase the maximum virtual contact stiffness that can be rendered to users without increasing the interface damping, this paper proposes a control strategy based on multirate wave communications between a haptic interface and a VE updated at a slow and fixed rate. The multirate wave communications are shown to be guaranteed passive only if the decrease of the wave sampling rate at the connection between the haptic interface and the VE does not cause aliasing. Therefore, an antialiasing low-pass filter is placed before the wave rate drop in the communications. The passivity condition is verified analytically and numerically for multirate haptic interaction in VEs with various contact stiffnesses and update rates. The transparency of haptic interaction in slow VEs to which users connect via passive multirate wave communications is investigated analytically in the frequency domain. Experiments validate that passive multirate wave communications can render stiffer contact in slow VEs than conventional direct coupling, and illustrate the destabilizing effect of the aliasing caused by the sampling rate drop in the communications.

Stable Haptic Rendering For Physics Engines Using Inter-Process Communication and Remote Virtual Coupling

Availability of physics engines has significantly reduced the effort required to develop interactive applications concerning the simulation of physical world. However, it becomes a problem when kinesthetic feedback is needed in the applications since the incorporation of haptic rendering is non-trivial, where fast haptic data update is demanded for stable rendering. In the regard, a framework for integrating haptic rendering into physics simulation engines is proposed. It mediates the update-rate disparity between haptic rendering and physics simulation engine by means of inter-process communication and remote virtual coupling, which fully decouples haptic rendering from complex physical simulation. Experimental results demonstrate that this framework can guarantee fast haptic rendering at 1k Hz even the physical simulation system operates at very low update rate. The remote virtual coupling algorithm shows better performance than the interpolation based methods in terms of stability and robustness.

Novel Method for Wind Estimation Using Automatic Dependent Surveillance-Broadcast

TWOmethods to acquire near real-time wind information can be distinguished [1–5]. The first method uses wind observations made by aircraft systems that are relayed to the ground. The second uses secondary surveillance radar (SSR) position and speed data, possibly extendedwith downlink airborne parameters (DAPs).When DAPs are unavailable, the SSR’s position and speed data can be used to estimate wind from aircraft that completed a turn [3,4]. This paper presents a novel method to estimate wind using Automatic Dependent Surveillance-Broadcast (ADS-B) over a larger area. ADS-B-equipped aircraft broadcast their position, ground speed, track angle, and other aircraft information [6,7]. Although registers for data in the air reference frame exist, data analysis showed these are left unused by most aircraft. For wind estimation purposes, ADS-B provides velocity vector information measured using a global satellite navigation system. This information can also be derived from SSR position data. However, the latter are expected to be, in most cases, less accurate and have a lower update rate. Previous methods were based on a single aircraft and therefore required multiple measurements of that aircraft at different headings. The proposed approach is new as it circumvents this limitation by assuming that aircraft at the same altitude travel, on average, at the same true airspeed (TAS) in all directions. The remainder of this note is organized as follows. Section II discusses the theoretical model and the application of dilution of precision (DOP) and Kalman filtering techniques to integrate noisy wind estimates into a time-varying wind profile for a larger area. Section III discusses the results of simulations to assess the effect of the actual wind speed and airspeed differences between aircraft. Section IV gives the results of a comparative analysis of wind estimates made using actual ADS-B datawith forecasts of the Global Forecast System (GFS). II. Wind Estimation Algorithm

Integrated GPS/INS navigation system with dual-rate Kalman Filter

A dual-rate Kalman Filter (DRKF) has been developed to integrate the time-differenced GPS carrier phases and the GPS pseudoranges with INS measurements. The time-differenced GPS carrier phases, which have low noise and millimeter measurement precision, are integrated with INS measurements using a Kalman Filter with high update rates to improve the performance of the integrated system. Since the time-differenced GPS carrier phases are only relative measurements, when integrated with INS, the position error of the integrated system will accumulate over time. Therefore, the GPS pseudoranges are also incorporated into the integrated system using a Kalman Filter with a low update rate to control the accumulation of system errors. Experimental tests have shown that this design, compared to a conventional design using a single Kalman Filter, reduces the coasting error by two-thirds for a medium coasting time of 30 s, and the position, velocity, and attitude errors by at least one-half for a 45-min field navigation experiment.

Study of ADS-B Data Evaluation

In western China, the terrain and meteorological conditions are so complex that it is not suitable to construct new radar stations. Automatic dependent surveillance-broadcast (ADS-B) is a totally new surveillance method, so before practically applied and operated in China, abundant tests and evaluations are necessary to validate the performance of ADS-B and guarantee the operational security. During the flight tests, we collect the data of radar, ADS-B and high accuracy position and compare the performance of ADS-B with radar based on high accuracy position. To solve the asynchronous problem among radar data, ADS-B data and real-time kinematic (RTK) data caused by different update rates, this article proposes the technique of synchronizing multi-surveillance data by extrapolating from the data of low update rate to high update rate according to velocity and heading. Meanwhile, because radar data, ADS-B data and RTK data are expressed in different coordinates and cannot be compared each other, this article provides a method to unifying the coordinates of multi-surveillance data. By the analysis and evaluation, we can conclude that the performance of ADS-B is better than radar.

A lightweight soft-state tracking framework for dense mobile ad hoc networks

In a mobile ad hoc network, tracking protocols need to deal with–in addition to the mobility of the target–the mobility of the intermediate nodes that maintain a track toward the target. To address this problem, we propose the MDQT (Mobility-enhanced Distributed QuadTree) tracking framework. MDQT employs a static cell abstraction to mask the mobility of the nodes and provide the illusion of a logical static network overlaid on the mobile network. MDQT implements this virtual static network layer in a lightweight/communication-free manner by exploiting the soft-state principle and the snooping feature of wireless communication. Through simulation, we study the impacts of the mobile node percentage and target mobility speed on the system performance. Simulation results show that the success rate of tracking is mostly unaffected by the speed of mobile nodes, but degrades slightly with the increases in mobile node percentage. On the other hand, the cost measurements (latency, average hops, and retry rate) are more sensitive to the mobility speed, and remain unaffected by the increase of mobile node percentage—owing to our soft-state design approach. We find that even at very high mobility speeds (50 m/s), low update rates (1 update per second), and 100% node mobility, the success rate of MDQT tracking is above 85% and the latency is comparable with that of static networks.

Hardware-based, Trajectory-Controlled Visual Servoing of Mobile Microrobots

Visual servoing based on camera or microscopic feedback has become a widely acknowledged technique for the positioning of robots. With a hardware-based image processing and tracking architecture, classic timing downsides such as low update rates, latency and jitter can be bypassed making visual servoing efficient. Applying this tracking to mobile nanohandling robots, a compact high-performance micro- and nanopositioning system is realized. Trajectory control becomes feasible due to the deterministic timing behavior of the position tracking as well as the reliable open-loop control of the robots. Measurement results demonstrate the excellent characteristics of the CMOS camera-based tracking system, the mobile nanohandling robots and the trajectory-controlled positioning. Although initially aimed at coarse positioning, the system achieves accuracies below 1 ±m.

Multiversion concurrency control for the generalized search tree

AbstractMany read‐intensive systems where fast access to data is more important than the rate at which data can change make use of multidimensional index structures, like the generalized search tree (GiST). Although in these systems the indexed data are rarely updated and read access is highly concurrent, the existing concurrency control mechanisms for multidimensional index structures are based on locking techniques, which cause significant overhead. In this article we present the multiversion‐GiST (MVGiST), an in‐memory mechanism that extends the GiST with multiversion concurrency control. The MVGiST enables lock‐free read access and ensures a consistent view of the index structure throughout a reader's series of queries, by creating lightweight, read‐only versions of the GiST that share unchanging nodes among themselves. An example of a system with high read to write ratio, where providing wait‐free queries is of utmost importance, is a large‐scale directory that indexes web services according to their input and output parameters. A performance evaluation shows that for low update rates, the MVGiST significantly improves scalability w.r.t. the number of concurrent read accesses when compared with a traditional, locking‐based concurrency control mechanism. We propose a technique to control memory consumption and confirm through our evaluation that the MVGiST efficiently manages memory. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Six-Degree-of-Freedom Haptic Rendering in Virtual Teleoperation

Six-degree-of-freedom (6-DoF) haptic rendering of the telerobotic operation method using virtual joint coupling (VJC) is proposed. This algorithm couples six joints of a virtual robot with those of a 6-DoF haptic device based on a spring-damper model to render force and torque feedback to a user and drive the virtual robot in the teleoperation simulation. Our rigid body dynamics is decoupled from the haptic rendering loop with an open dynamic simulation library Open Dynamics Engine, which runs at a lower update rate, thereby alleviating computation demand and improving the stability of the system. To illustrate the role of haptics and physically based simulation in teleoperation, a path-following experiment with virtual constraints is carried out. An experiment of virtual assembly, in which a user performs assembly tasks by means of manipulation of a gripper mounted at the end of a virtual robot, is also implemented to verify the VJC algorithm.

46.2: Real‐Time Pen Tracking on Electronic Paper Displays

AbstractOn most electronic paper displays (EPDs), low update rates lead to a poor user experience especially for pen‐based markups. The slow update causes a remarkable delay between pen motion and visibility of the stroke. Even worse, this delay varies depending on the current part of the update cycle. This paper presents a real‐time pen tracking method for EPDs, using a new display driver on an unmodified E Ink hardware platform. This method compares favorably to the iLiad E‐Reader.